It has been heretofore proposed to provide vehicle wheel lug nuts which are coded to a special wrench so as to prevent theft of vehicle wheels. A typical example of heretofore proposed arrangements of this kind is disclosed in U.S. Pat. No. 3,241,408, issued Mar. 22, 1966 to Lewis D. McCauley. This patent discloses a nut formed with a recess having a curvilinearly extending channel that receives a wrench formed with a complimentary flange. Such heretofore proposed arrangements have not been completely practical to manufacture because of the cost of fabricating the curvilinear engaging surfaces of the lock nuts and their wrenches. Moreover, the utilization of such curvilinear surfaces has made it difficult to apply and remove the wrench from the wheel nut, such curvilinear surfaces tending to become jammed. In many cases the wrench would break off inside the nut recess.